Myxicola infundibulum (Renier,
1804)

Common name(s): Slime tube worm, slime feather duster

A colony of Myxicola infundibulum
on the side of a dock. The colony is about 30 cm across and each
funnel-like set of radioles
is about 2.5-3 cm across. The entire colony is a ball of mucus that
remains when the animals withdraw rapidly into their slime tubes.

(Photo by: Dave Cowles, July 2014)

Description: Like all members of
Family
Sabellidae (parchment tube worms), this species has a plume of pinnate,
featherlike radioles
on its head region and lives in a flexible, leather or parchment-like tube
it has secreted. Like serpulids
(calcareous tubeworms), the head has a series of pinnateradioles with which
the animal suspension feeds. Unlike serpulids,
the radioles are not
spiraled but form a series of semicircles around the head region.
In Myxicola infundibulum
none of the radioles
have conspicuous ocelli
curled around them near their tips (The do, however, have ocelli,
as demonstrated by their rapid withdrawal into their tube when a shadow
passes over them). Unusually, the proximal part of the radioles
are connected to one another by a membrane so that they form a funnel (photo).
The thorax is longer
than in most local sabellids--8 setigers
(setae-beaering segments).
The first 5 or 6 thoracicneuropodia
have long-handled uncini
(not avicular
uncini) and no pickaxe-shaped setae.
The abdominaluncini
occur in rows that extend much of the way around the segments and they
have several apical teeth.
They secrete gelatinous tubes of mucus. The color of the plume of
radioles
is yellow to greenish, brown, or brownish-purple. Worm is up to 9
cm long.

How to Distinguish from Similar Species:
The membrane which connects the base of the radioles,
forming them into a funnel, is a distinctive feature of this species when
combined with abdominaluncini
which form bands nearly around the body. A second, related slime-tube
worm, M. asthetica, has also
been reported to be in the region. It has only 1-4 thoracicsetigers
and a single
apical tooth
on the abdominaluncini,
and it often attaches to ropes.

Geographical Range: Pacific coast
of North America from the Bering Sea to California and in the Atlantic
Ocean and Mediterranean Sea.

Depth Range: Intertidal to 425
m.

Habitat: In rock crevices or on
floats. Sometimes buried in soft mud.

Biology/Natural History: These
worms are often found as an aggregation in which the individual members
secrete so much slime that they make a boulder-shaped colony. They
withdraw rapidly into the clear mucus tubes when disturbed or when a shadow
passes over. Silt and small debris may cover the mucus, masking its
transparency (photo). At other times,
they build their mucus tubes wedged between other species of worms, mussels,
or tunicates.

This species can withdraw into its mucus tube very rapidly, by use of
a giant ventral axon. That axon extends throughout the length of
the body and has been the subject of much research on neural activity.
It comprises 27% of the animal's entire nervous system. Nerve impulses
travel at 6-20 m/s along the axon. The quick withdrawal into the
tube not only shelters the worm from predators but forcefully ejects wastes
from the tube.

Unlike in some other sabellids, the
crown of radioles is
not autotomized to escape predators, and if the animal loses its radioles
it will likely die. Previous authors have claimed that this species
cannot regenerate, but this has been disproven more recently, at least
in specimens from the Mediterranean Sea (Licciano
et al., 2015)

The name 'Myxicola' means 'living in slime' and 'infundibulum' refers
to the funnel shape formed by the radioles.